Retractable surgical knife

ABSTRACT

A retractable &#34;ball-pen&#34; like tool/scalpel having a latch mechanism is automatically retracted when not in use by pushing the latch mechanism and is extended when in use by pushing a tool/blade support member of the tool/scalpel. The latch mechanism is engaged with the tool/blade support member when the tool/blade support member is pushed to an operative position wherein a tool/blade is exposed from a sheath member. The latch mechanism is pushed transversely and disengaged with the tool/blade support member whereby the tool/scalpel is retracted into the sheath member. A key member having a post is mounted on a back end of the sheath member. The post and the latch mechanism prevent the key member from falling out of the back end of the sheath member. Almost all the parts of the tool/scalpel can be made of plastic materials.

This is a continuation-in-part application of the application, Ser. No.08/489,890, filed Jun. 13, 1995, now U.S. Pat. No. 5,562,282, which is acontinuation-in-part application of the application, Ser. No.08/161,662, filed Dec. 3, 1993, now U.S. Pat. No. 5,423,843, which is acontinuation-in-part application of the application, Ser. No.07/986,139, filed Dec. 4, 1992, now U.S. Pat. No. 5,292,329.

FIELD OF THE INVENTION

The present invention relates generally to retractable scalpels andsimilar devices which have a tool/blade movable between an exposedoperative position and a covered nonoperative position. In oneembodiment, the invention relates to a protective retractable scalpel inwhich the blade is extended against the force of a spring to expose acutting surface, and upon completion of the activity, the cuttingsurface of the blade is quickly and automatically retracted into asheath.

BACKGROUND OF THE INVENTION

Scalpels are a class of knives used in the surgical environment forincising, stabbing, shaving, and curetting of human and animal tissue.Conventional scalpels used for this purpose have a stationary blade. Theblade is always exposed thereby creating a hazard of inadvertentpuncture to an operating team member and to any other person who maycome in contact with an instrument. The primary hazard of puncture isthe possible transmission of an infectious agent, such as the AIDSvirus. It has long been a desire of the medical profession to provide aprotective scalpel which completely and absolutely encircles andprotects the blade during non-use.

In some emergency situations, a surgeon must work quickly and handinstruments back and forth to assistants. It is dangerous sometimesbecause the sharp scalpels can accidentally cut or jab the personnel'shands during the operation. Certain fatal infections can be transferredto individuals through small cuts.

Presently existing protective scalpels have removable guards to preventcontact with the blade during non-use. However, with the rapidity inwhich surgery is conducted, this imposes a degree of inconvenience whichwould be burdensome. Other conventional protective scalpels includeexamples in which a blade sheath pivots or extends and retracts upon agiven force applied to a handle of the scalpel. These scalpels do notprovide absolute security of the blade such as the present inventionwhere the blade is completely encased in a sheath.

Prior art tool retraction/latch mechanisms have the disadvantage ofexposed screws, springs, fasteners, gears, links, and the like which,upon certain conditions, could loosen and fall into a wound or cavity.

Another disadvantage of many protective scalpels is the encroachment ofa portion of the scalpel blade. This interfaces with normal use of thescalpel, as entire length of the blade is typically used.

Examples of known prior art are:

U.S. Pat. No. 3,657,812 which discloses a retractable tool holder;

U.S. Pat. No. 5,071,426 which discloses a surgical scalpel with aretractable blade guard;

U.S. Pat. No. 5,116,351 which discloses a safety scalpel having a bladeprotecting sheath;

U.S. Pat. No. 5,139,507 which discloses a surgical scalpel with aretractable blade guard; and

U.S. Pat. No. 5,141,517 which discloses a retractable instrumentautomatically actuating the instrument to extend forward from aprotective sheath.

The present invention solves many of the problems associated with priorart scalpels and latch mechanisms.

SUMMARY OF THE INVENTION

The present invention provides a tool holder in which a tool retractsinto a chassis of the tool holder when not in use such that the tool isshielded.

In one embodiment, it is specifically intended that this tool be ascalpel which functions much like a typical retractable ball point penwith its simple actuation and detent type of release.

One advantage of one embodiment of the present invention is to provide ascalpel having a retractable blade which is relatively inexpensive toproduce.

One advantage of the present invention is to provide a scalpel that isfree of encumbrance long the entire length of the blade in its extendedoperative position.

In one embodiment of the present invention, there is provided a scalpel,in either an extended or a retracted position, which has no element orpart, such as a pin, screw, fastener, link, or spring, that could becomedislodged and be lost in a patient's tissues or body cavity.

In one embodiment of the present invention, the retractable scalpelcomprises a tubular sheath member and a tubular blade support memberwhich are secured together by a locking collar.

In one embodiment, the blade support member is slidably mounted andpartially disposed in the sheath member. A cutting blade, connectible toone end of the blade support member, is shielded in the sheath memberwhen the scalpel is not in use. The blade is extended from the sheathmember and exposed when the scalpel is in its operative position.

Still in one embodiment, when the scalpel is in its operative position,the blade support member is forced forward against the strain of aspring and is locked by a latch mechanism. The blade support member isautomatically released by deactuating the latch mechanism when thescalpel is not in use. Accordingly, when the blade support member isforced forward, the cutting blade extends from the sheath member. Whenthe blade support member is released backward, the cutting bladeretracts into the sheath member.

Further in one embodiment, a first spring is disposed between a back endof the blade support member and proximate the back end of the sheathmember. The spring is compressed in the operative position.

In one embodiment, the blade support member comprises a pair oftransversely elongated and longitudinally extended slots wherein one ofthe slots is disposed at a top side and another slot is disposed at abottom side of the blade support member. When the scalpel is made intoits operating position, the latch mechanism is longitudinally slid alongthe slots, and is received in an enlarged slot portion disposedproximate a back end of the top side slot.

Still in this embodiment, the latch mechanism includes an upper section,an enlarged section integrated with the upper section, and a lowersection. A second spring is compressed under the upper section when thescalpel is not in use. The enlarged section is received into theenlarged slot portion by sliding and pushing the blade support membertoward a front end of the blade support member. Upon the receipt of thelatch mechanism enlarged section into the enlarged slot portion, thefirst spring is compressed and the already compressed second springextends so as to force the enlarged section into the enlarged slotportion so as to lock the blade support member in place.

Still in this embodiment, the latch mechanism is deactuated bytransversely compressing the second spring to separate the enlargedsection from the enlarged slot portion. The first spring extendsbackward so as to retract the blade into the sheath member wherein thescalpel is not in use. The latch mechanism serves an additional functionin that it prevents the scalpel from rolling more than 180° on asurface.

Furthermore, in one embodiment, a limiting pin and a stop pin aredisposed on each side of the latch mechanism which are used to limit theblade extending movement of the blade support member and to stop theblade retracting movement of the blade support member, respectively.

In one embodiment, the blade is removably and securely attached into theblade support member by a blade receiving portion and a fitting member.

In one embodiment, the scalpel is made of stainless steel or anydisposable plastic material.

Yet in one embodiment, a plurality of holes are disposed on top andbottom sides of the sheath member so that it reduces the weight of thescalpel, as well as easily washes away blood products from the bladeduring non-use.

Further in one embodiment, the front end of the sheath member isbeveled.

Yet in one embodiment, an external surface of the sheath member isknurled so that the operator can easily control the scalpel during theoperation.

In another embodiment, a latch mechanism comprises a tubular memberhaving two aligned longitudinal slots, a key member partially disposedin the tubular member, and a rod. The rod engages with the tubularmember and the key member when the scalpel is in use by pushing theblade support member toward the latch mechanism and disengages from thetubular member and the key member when the scalpel is not in use bytransversely pushing the tubular member.

Still in another embodiment, a pin connects two opposite walls of thetubular member beside the two slots. An axis of the pin is perpendicularto a longitudinal axis of the tubular member and is perpendicular to alongitudinal axis of the sheath member. A second spring is disposed inthe tubular member between a top end of the tubular member and the pin.When the scalpel is in use, the rod is engaged between the pin and thekey member by compressing the first spring, and the second spring isfurther compressed by the top end of the tubular member. After the pindrops into a notch of the rod, the second spring is released by the topend of the tubular member, and the scalpel is locked in an operativeposition. When the scalpel is not in use, the second spring iscompressed by pushing the tubular member downward, the pin is disengagedfrom the notch of the rod, and the rod is retracted from the tubularmember and the key member by an expanding force of the first spring.

Yet in another embodiment, the key member includes a prong portionhaving top and bottom prongs. The top prong is transversely disposed inthe slots between the pin and a bottom end of the second spring, thusthe second spring is compressed between the top prong and the top end ofthe tubular member. The bottom prong is transversely disposed in theslots between the pin and a bottom end of the tubular member. The topand bottom prongs relatively reciprocate in the slots of the tubularmember.

Still in another embodiment, the key member includes an arm portionhaving top and bottom arms being integral with the top and bottom prongsrespectively by a connecting portion. The connecting portion has acentral hole whereby the rod passes through while engaged. The armportion and the connecting portion are disposed outside of the slots,and the first spring is disposed between the back end of the toolsupport member and a back end of the connecting portion. When thescalpel is in use, the first spring is compressed between the back endof the blade support member and the connecting portion, and the rodpasses through the space between the top and bottom arms and the centralhole of the connecting portion until the rod is engaged with the pin ofthe tubular member.

Further in another embodiment, the rod has a tapered front portion. Thenotch is disposed beside the tapered front portion. When the rod ispushed toward the key member, the tapered front portion passes throughthe central hole and pushes the pin downward by compressing the secondspring by the top end of the tubular member, and the movement of the rodis stopped by dropping the pin into the notch. When the tubular memberis pushed downward to disengage the pin from the notch, the rod isretracted from the tubular member and the key member by an expandingforce of the first spring.

Still in another embodiment, the tapered front portion has a tip and aramp surface engaging with the pin.

Still in another embodiment, the central hole is aligned with the spacebetween the pin and the top prong when the tapered front portion of therod passes through the space.

Further in another embodiment, the top and bottom prongs relativelyreciprocate in the aligned longitudinal slots, and the relativelyreciprocating movement of the prongs is limited by two ends of theslots.

Still in another embodiment, the latch mechanism includes fewer workingparts. This provides simpler manufacture as well as making a disposableunit possible with existing technology.

Yet in another embodiment, the latch mechanism substantially eliminatesfriction forces. The elimination of friction allows safer operation aswell as the correct feel of an instrument.

Still in another embodiment, the tool holder includes fewer workingparts. This results in a clearer appearance of the tool.

In the second embodiment, the two transverse drill holes of the firstembodiment around the top and bottom openings of the sheath member arecompletely eliminated. In addition, the limiting pin, the stop pin, andthe locking collar are eliminated in the second embodiment.

In a third embodiment, a blade support member has a second rod which isattached to a back end of a blade receiving portion of the blade supportmember. Alternatively, the rod is a part of the blade receiving portionwhich is disposed at its back end. The second rod engages with thetubular member and the key member after the blade is retracted into thesheath member, i.e., the scalpel is not in use. When the blade isretracted into the sheath member by a return force of the first spring,the second rod is engaged with the latch mechanism between the pin andthe key member by a residual force of the return force. Accordingly, theblade support member and its mounted blade are locked in place when theyare retracted into the sheath member. In addition, the pin stops anyfurther movement of the blade support member.

Still in the third embodiment, the second rod acts in a similar manneras the first rod when the first rod engages between the pin and the keymember as the scalpel is in use.

Further in the third embodiment, a compression third spring is disposedoutside the second rod behind a shock absorber. The third compressionspring is compressed between the shock absorber and the outer wall ofthe latch mechanism when the second rod is locked in the latchmechanism. Accordingly, the third compression spring also functions asan absorber when the blade is retracted.

Yet in the third embodiment, to extend the blade out of the sheathmember, the latch mechanism is first pushed downward to release thesecond rod from the locking position. The third compression spring alsohelps the second rod release from the locking position when the latchmechanism is pushed downward.

In a fourth embodiment, there is no compression spring disposed outsidethe second rod. When the scalpel is in use, the latch mechanism issimply pushed downward to unlock the second rod. The blade supportingmember can then be pushed forward to extend the blade out of the sheathmember.

In a fifth embodiment, the second compression spring disclosed in thefirst embodiment, which is disposed inside the latch mechanism, iseliminated. Instead, a compression spring is disposed around the outsidewall of the latch mechanism. The outside wall is configured to adapt tosuch a compression spring which functions in a similar manner as thesecond compression spring in the first embodiment. Accordingly, thecompression spring allows the latch mechanism to lock/unlock the firstor second rod.

Further in the fifth embodiment, the bottom end of the latch mechanismis beveled so as to allow easy assembly during the assembly of thescalpel.

In a sixth embodiment, the compression spring of the fifth embodiment isreplaced by a leaf spring. The leaf spring is mounted on or integral tothe top end of the latch mechanism. The two legs of the leaf springbiasedly engage with the outside wall of the sheath member when thelatch mechanism is activated.

In an alternative embodiment, a post is disposed on the top surface ofthe top prong of the key member. The compression spring of the latchmechanism is assembled to be disposed around the post so as to preventthe key member from falling out of the latch mechanism, e.g., fromdropping off the sheath member. The post can be integrally molded withthe top prong of the key member.

Still in this alternative embodiment, the back portion of the sheathmember has an open end slot to allow the post to pass by during theassembly.

Yet in this alternative embodiment, the top and bottom prongs areidentical.

In one embodiment, the scalpel is made of plastic materials, such asPVDF, except the blade being made of metal or metals. The springs can bemade of metal or metals. In one embodiment, the springs are made ofplastic materials, or are coated with a microfilm (e.g. Teflon™) orother types of polypropylene materials so that the springs areheat/steam resistent and chemical resistent. Accordingly, almost allparts of the scalpel can be injection molded.

One advantage of the injection molded scalpel is very light. The plasticparts of the scalpel are easy and inexpensive to make. Further, theplastic parts can be disposable after the use.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing in which like reference numerals and letters generallyindicate corresponding parts throughout the several views,

FIG. 1 is a perspective view of an embodiment of a retractable scalpelin accordance with the principles of the present invention when thescalpel is in an inoperative retracted position.

FIG. 2 is a perspective view of the scalpel shown in FIG. 1 when thescalpel is in an operative extended position.

FIG. 3 is a longitudinal cross-sectional view of the scalpel shown inFIG. 1 when the scalpel is in an inoperative position.

FIG. 4 is a longitudinal cross-sectional view of the scalpel shown inFIG. 2 when the scalpel is in an operative position.

FIG. 5 is an exploded assembly view of the scalpel shown in FIG. 1.

FIG. 6 is a perspective view of a second embodiment of a retractablescalpel in accordance with the principles of the present invention whenthe scalpel is in an inoperative retracted position.

FIG. 7 is a perspective view of the second embodiment of the scalpelwhen the scalpel is in an operative extended position.

FIG. 8 is a longitudinal cross-sectional view of the second embodimentof the scalpel when the scalpel is in an inoperative position.

FIG. 9 is a longitudinal cross-sectional view of the second embodimentof the scalpel when the scalpel is in an operative position.

FIG. 10 is an enlarged perspective view of a key member in the secondembodiment of the scalpel.

FIG. 11 is an enlarged side view of a rod in the second embodiment ofthe scalpel.

FIG. 12 is a perspective view of the second embodiment of the scalpelbeing operated by an operator's hand.

FIG. 13 is a perspective view of the second embodiment of the scalpelbeing about inoperative by an operator's hand.

FIG. 14 is a partial longitudinal cross-sectional view of the third andfourth embodiments of the scalpel when the scalpel is in an inoperativeposition.

FIG. 15 is a schematic view of a fifth embodiment of the scalpel showinga latch mechanism having an outside compression spring.

FIG. 16 is a schematic view of a sixth embodiment of the scalpel showinga latch mechanism having an outside leaf spring.

FIG. 17 is an enlarged perspective view of an alternative embodiment ofthe key member.

FIG. 18 is a perspective view of the scalpel while using the alternativeembodiment of the key member, with the scalpel being in an operativeextended position.

FIG. 19 is a longitudinal cross-sectional view of the scalpel shown inFIG. 18 when the scalpel is in an inoperative retracted position.

FIG. 20 is a longitudinal cross-sectional view of the scalpel shown inFIG. 18 when the scalpel is in the operative extended position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, there is shown in FIGS. 1-5 a first embodimentof a retractable scalpel, designated 40, generally in accordance withthe principles of the present invention.

The scalpel 40 broadly comprises a tubular barrel or sheath member 42and a blade support assembly 44 including an inner tubular blade supportmember 45 which is received telescopically within the sheath member 42.A surgical blade 46, which is mounted on a front end 48 of the bladesupport assembly 44, is shielded in the sheath member 42. A plurality ofholes 50 are disposed on a top side and a bottom side (not shown) of thesheath member 42. The surgical blade 46 is in communication with outsidethrough the holes 50. Accordingly, the holes reduce the weight of thescalpel 40 as well as facillitatively washing away blood products fromthe blade 46.

The blade support member 45 includes a pair of longitudinally extended,diametrically opposed slots 52,53 wherein the slot 52 is disposed at atop side of the blade support member 45 and the slot 53 is disposed at abottom side (shown in FIGS. 3, 4) of the blade support member 45. Anenlarged slot portion 54 is disposed proximate a back end 56 of the topside slot 52, a portion of the slot 52, shown as a slot portion 52a inFIGS. 3 and 4, extending beyond the enlarged slot portion 54. The slot53 also extends beyond the enlarged slot portion 54. The enlarged slotportion 54 is able to receive a larger diameter member than the otherportion of the top side slot 52. Further, upon receipt of the largerdiameter member, which has the diameter larger than the top side slot 52but smaller than the enlarged slot portion 54, into the enlarged slotportion 54, the member is longitudinally locked relative to the sheathmember 42 and the blade support member 45.

A spring 58, which is received between a diameter reducing end cap 60(see FIG. 3) of the blade support member 45 and a limiting pin 61 at theback end 62 of the sheath member 42, is visible from outside through theslots 52, 53. The spring 58 is compressed or released between thelimiting pin 61 and the end cap 60 when the blade support assembly 44 isslidably moved relative to the sheath member 42.

A latch mechanism 64 is disposed proximate the back end 62 of the sheathmember 42. The latch mechanism 64 includes a push button section 66, aspring 76 and a bottom section 65 which comprises a bottom pin section67, a flange section 69 and a hollow section 71. The push button section66 transversely projects from the top side slot 52 and a top opening 68of the sheath member 42, while the bottom pin section 67 projects fromthe bottom side slot 53 and a bottom opening 70 in the sheath member 42which is diametrically opposite to the top opening 68 (shown in FIG. 3).The openings 68,70 are in transverse alignment with the slots 52,53wherein the diameter of the top opening 68 is larger than the top sideslot 52 and the diameter of the bottom opening 70 is smaller than theslots 52,53.

A locking collar 72 receives the latch mechanism 64, and locks the latchmechanism 64, the sheath member 42 and the blade support assembly 44together. The structure of the locking collar 72 will be discussedlater.

Now referring to FIG. 2, the blade 46 is shown extending from the sheathmember 42 in the operative position. The blade support assembly 44 ispushed toward a front end 74 of the sheath member 42 and the spring 58is compressed accordingly. The front end 74 of the sheath member 42 isbeveled. Thus, the whole portion of the blade 46 which contacts acutting piece (not shown) is wholly exposed so that the surgeon can havea larger view of the cutting piece.

FIGS. 3 and 4 show longitudinal cross-sectional views of FIGS. 1 and 2respectively, wherein the blade 46 is shielded under the sheath member42 in FIG. 3 when the scalpel is in the retracted, inoperative position,while the blade 46 is projected from the sheath member 42 in FIG. 4 whenthe scalpel 40 is in the extended, operative position.

In FIG. 3, the spring 76 is compressedly disposed under the push buttonsection 66 and received in the hollow section 71 of the latch mechanism46. An enlarged section 78 of the push button section 66, has a largerdiameter than the top side slot 52 but smaller than the diameter of theenlarged slot portion 54. Thus, the enlarged section 78 is disposedunderneath the top side slot 52 as well as the top opening 68 of thesheath member 42. Accordingly, the spring 76 is kept compressed betweenthe push button section 66 and the bottom section 65 when the scalpel 40is not in use. As mentioned above, the push button section 66 projectsthrough the top side slot 52 and the top opening 68 of the sheath member42, while the bottom pin section 67 projects from the bottom side slot53 and the bottom opening 70 of the sheath member 42.

Now referring to FIG. 4, there is shown a cross-sectional view of thescalpel 40 having the blade extended from the sheath member 42. Theblade support assembly 44 is slidably moved toward the front end 74 ofthe sheath member 42 during which the enlarged section 78 is able toalign with the enlarged slot portion 54. When the enlarged section 78aligns with the enlarged slot portion 54, the enlarged section 78 isautomatically received into the enlarged slot portion 54 of the bladesupport member 45 as well as the top opening 68 as a result of thespring 76 extending. Thereupon, the latch mechanism 64 stops thelongitudinal movement between the sheath member 42 and the blade supportassembly 44.

The latch mechanism 64 is disposed between the limiting pin 61 and astop pin 80. The stop pin 80 is aligned with the slots 52,53. The stoppin 80 engages a front end 49 of the slots 52, 53. Thus, the stop pin 80reduces the possibility of damages of the latch mechanism 64. Uponpushing the push button section 66, the enlarged section 78 isaccordingly pushed away from the enlarged slot portion 54 so as to allowthe longitudinal movement between the sheath member 42 and the bladesupport assembly 44. Therefore, the blade support assembly 44 isautomatically released backward so as to retract the blade into thesheath member 42.

Now referring to FIG. 5, an exploded view of scalpel 40 is shown. Thelocking collar 72 includes a L-shape slot 82 on a top side of thelocking collar 72, and an opening 84 (shown in FIGS. 3, 4) on a bottomside of the locking collar 72. The push button section 66 is received ina slot terminal point 86 which is disposed at one end of the L-shapeslot 82. The bottom pin section 67 projects outside through the bottomopening 84. The diameter of the opening 84 is smaller than that of theslot terminal point 86 so that the opening 84 receives a smaller size ofthe bottom pin section 67, while the slot terminal point 86 receives alarger size of the push button section 66. Consequently, the L-shapeslot 82 secures the sheath member 42, the blade support assembly 44 andthe latch mechanism 64 together. Further, the slot terminal point 86 issmaller than the diameter of the enlarged section 78 of the latchmechanism 64. Thus, the locking collar 72 retains the latch mechanism 64in place on the scalpel 40.

Now referring to the blade 46 and its mounting mechanism. A bladereceiving portion 88, having a needle-like head 89, includes alongitudinal projection 90 which is received into a corresponding slot92 on the blade 46. A through hole 94 which is disposed on the bladereceiving portion 88 aligns with a corresponding through hole 96 on afitting portion 98 and further aligns with a corresponding through hole100 on the blade support member 45. A pin 102, having a length the sameas the diameter of the blade support member 45, passes through thethrough holes 94,96 and 100 so as to secure the blade 46 onto the bladesupport member 45. The blade receiving portion 88 can be replaced byremoving the pin 102. A back portion 104 of the blade receiving portion88 is received in a bore 106 of the fitting portion 98. The bladereceiving portion 88 and the fitting portion 98 are standard anduniversal which are able to receive most regular scalpel blades. It willbe appreciated that various blade mounting detach mechanisms might beused.

The limiting pin 61, having a length the same as the diameter of thesheath member 42, passes through a pair of transversely oppositeopenings 108 in the sheath member 42 and extends into the slot portion52a and the slot 53. The stop pin 80, having a length the same as thediameter of the sheath member 42, passes through a top opening 110 and atransversely opposite bottom opening 112 in the sheath member 42. Thestop pin 80 has a top portion larger than a bottom portion which arerespectively received in the larger top opening 110 and the smallerbottom opening 112.

The scalpel 40 is made of stainless steal in the preferred embodiment.Alternatively, the scalpel 40 can be made of any kind of metal orplastic materials.

Further, an external surface 114 of the sheath member 42 is knurled sothat the surgeon can easily grab or control the scalpel 40 during theoperation.

When the scalpel 40 is in use, the blade support assembly 44 is pushedforward. The blade 46 is exposed outside of the sheath member 42accordingly. The scalpel 40 is locked into an operative position whenthe enlarged section 78 engages with the enlarged slot portion 54.

When the scalpel 40 is not in use, the push button section 66 is pushedtransversely. The blade support assembly 44 is automatically retractedand the blade 46 is accordingly shielded in the sheath member 42.

In assembling the scalpel 40, the longitudinal projection of the bladereceiving portion 88 is received in the slot 92 of the blade 46. Theblade receiving portion 88 is placed into the bore 106 of the fittingportion 98. The spring 58 is inserted and disposed at the end cap 60.The blade 46, the blade receiving portion 88 and the fitting portion 98are inserted into the front end 48 of the blade support member 45. Thethrough holes 94, 96 and 100 are aligned to each other and receive thepin 102 therebetween. Thus, the blade assembly 44 is formed.

The blade support assembly 44 is then slidably inserted into the sheathmember 42 until the slots 52, 53 align with the openings 68, 70,respectively. The pins 61, 80 are inserted into the openings 108 and110,112, respectively. The bottom section 65, the spring 76 and the pushbutton section 66 are inserted in the slots 52,53 and the enlarged slotportion 54 from the top opening 68 to the bottom opening 70. The bottompin section 67 is received in the bottom opening 70 while the flangesection 69 stops the further insertion of the bottom pin section 67. Thespring 76 is positioned in the hollow section 71 between the bottom pinsection 67 and the push button section 66. At this moment, the enlargedsection 78 is disposed outside of the top side slot 52. The bladesupport assembly 44 is pushed to allow the enlarged section 78 aligningwith the enlarged slot portion 54 so that the enlarged section 78 isable to move underneath the top side slot 52. The bottom pin section 67is pushed into the bottom side slot 53 to allow the locking collar 72 toslide over the latch mechanism 64. The locking collar 72 is slid overthe back end of 62 the sheath member 42. The locking collar 72 is movedalong the L-shaped slot 82 to the position where a clockwise rotation ofthe locking collar 72 is allowed. Then the locking collar 72 is rotatedin a clockwise manner to allow the latch mechanism 64 slide into theslot terminal point 86. The push button section 66 is received in theslot terminal point 86, while the bottom pin section 67 projects throughthe bottom side slot 53, the bottom opening 70 of the sheath member 42and the bottom opening 84 of the locking collar 72. Upon this step, thescalpel 40 is assembled.

The scalpel 40 can be disassembled following the reverse procedures ofassembling the scalpel 40.

The blade 46 can be replaced by any type of standard scalpel blade. Inreplacing the blade 46, the blade 46 is simply removed from thelongitudinal projection 90 of the blade receiving portion 88.

Referring to FIGS. 6-13, there is shown a second embodiment of aretraction scalpel, designated by the reference numeral 140, generallyin accordance with the principles of the present invention. In FIG. 6,the scalpel 140 includes a sheath member 142 and a blade support member144. The blade support member 144 is telescopically partially receivedin the sheath member 142 from a back end 146 of the sheath member 142.The sheath member 142 has two aligned transverse holes 148,150 proximatethe back end 146. A latch mechanism 152 is transversely partiallydisposed between the holes 148,150 of the sheath member 142. A firstspring 154 is disposed inside the blade support member 144. A rod 155 istelescopically disposed in the spring 154. When the scalpel 140 is notin use as shown in FIG. 6, a blade 156 (see FIG. 8) which is mounted onthe front of the blade support member 144 is retracted into the sheathmember 142. The spring 154 is released in the blade support member 144.It is preferred that the same mounting means as disclosed in the firstembodiment is used to mount the blade 156 onto the blade support member144. It is appreciated that any other types of mounting means can beused in the second embodiment.

The blade support member 144 has top and bottom longitudinally alignedslots 158,160. The bottom slot 160 is shown in FIG. 8. The rod 155 whichis displayed through the top and bottom slots 158,160 is integral to theback end of the blade support member 144. The latch mechanism 152relatively reciprocates in the longitudinally aligned slots 158,160between front and back ends of the slots 158,160.

In FIG. 7, the scalpel 140 is in an operative position. The blade 156 isextended from the sheath member 142. The blade support member 144 ispushed toward the latch mechanism 152, whereby the spring 154 iscompressed. The latch mechanism 152 locks the scalpel 140 in anoperative position.

FIGS. 8 and 9 show longitudinal cross-sectional views of the scalpel 140being in the inoperative position and the operative position,respectively.

In FIG. 8, the latch mechanism 152 includes a tubular member 162 whichhas a head portion 164 extending out of the hole 148, a foot portion 166extending out of the hole 150, and a middle portion 168 beingsubstantially disposed in the sheath member 142. The middle portion 168has two slots 170,172 and two walls beside the slots 170,172. The lengthof the slots 170,172 is larger than the outer diameter of the bladesupport member 144 so that the blade support member 144 is able to passthrough the latch mechanism 152 to expose the blade 156 from the sheathmember 142.

The tubular member 162 further includes a pin 174 which is horizontallydisposed between the two walls beside the slots 170,172. The axis of thepin 174 is perpendicular to the longitudinal axis of the tubular member162 and is perpendicular to the longitudinal axis of the scalpel 140 sothat the pin 174 becomes an obstacle for the rod 155 to pass through thetubular member 162.

A second spring 176 is received in the tubular member 162. The top endof the spring 176 is attached to a top closed end 178 of the tubularmember 162. The bottom end of the spring is disposed above the pin 174.

The latch mechanism 152 further includes a key member 180 (see detailsin FIG. 10). The key member 180 includes a prong portion 182 having topand bottom prongs 184,186, an arm portion 188 having top and bottom arms190,192 which are integral with the top and bottom prongs 184,186,respectively, by a connecting portion 194. The connecting portion 194includes a central hole 196 whereby the rod 155 passes through. Theouter surfaces of the arm portion 188 and the connecting portion 194 areof the same cylindrical contour. The bottom prong 186 has an outersurface aligned to the outer surface of the connecting portion 194 anddesigned to have the same contour as the outer surface of the connectingportion 194. The top prong 184 has a substantially flat outer surface.The flat outer surface of the top prong 184 is lower than the outersurface of the connecting portion 194. The top and bottom arms 190,192have rear flanges 198,200, respectively.

Still in FIG. 8, the top prong 184 is vertically disposed in the slots170,172 between the pin 174 and the bottom end of the second spring 176.The bottom prong 186 is vertically disposed in the slots 170,172 betweenthe pin 174 and the bottom end of the slots 170,172. The second spring176 is compressed between the top prong 184 and the top end 178 of thetubular member 162, and the bottom prong 186 is engaged with the bottomend of the slots 170,172. The space between the top and bottom prongs184,186 are smaller than the length of the slots 170,172 so that theprongs 184,186 are relatively movable toward the top end of the slots170,172 by further compressing the second spring 176. The space betweenthe pin 174 and the highest reaching point of the top prong 184 in theslots 170,172 is large enough for the rod 155 to pass through. Theconnecting portion 194 and the arm portion 188 are disposed outside ofthe slots 170,172. The key member 180 is disposed inside of the sheathmember 142 except the rear flanges 198,200 are engaged with the back end146 of the sheath member 142. The external surfaces of the flanges198,200 have the same contour as the external surface of the sheathmember 142. Thus, the tubular member 162 and the key member 180 aredetachably engaged with proximate back end 146 of the sheath member 142.

The first spring 154 is disposed between the back end of the bladesupport member 144 and the back end of the connecting portion 194. Whenthe blade support member 144 is pushed toward the latch mechanism 152,the first spring 154 is compressed and is partially disposed in thespace between the top and bottom arms 190,192 (see FIG. 9). Accordingly,the space between the top and bottom arms 190,192 becomes a spring well.The connecting portion 194 also takes the shock against the latchmechanism 152 when the blade support member 144 is pushed toward thelatch mechanism 152.

As shown in FIG. 9, the rod 155 is pushed toward the latch mechanism152. The rod 155 includes a tapered front portion 202 having a tip 204pointed to the latch mechanism 152. A ramp surface 206 which facestoward the bottom of the latch mechanism 152 is followed the tip 204.The rod 155 further includes a notch 208 rearward of the end of the rampsurface 206. It is preferred that the depth of the notch 208 is abouthalf of the rod diameter. It is appreciated that a different depth canbe used.

When the blade support member 144 is pushed toward the latch mechanism152, the first spring 154 is compressed, and the tapered front portion202 passes through the space between the top and bottom arms 190,192,the central hole 196, and engages with the pin 174. The pin 174 ispushed downward by the ramp surface 206. The second spring 176 isfurther compressed by the top end 178 of the tubular member 162. Afterthe pin 174 slides over the notch 208, the pin 174 is moved upward bythe compressed force of the second spring 176. Accordingly, the pin 174drops into the notch 208 and engages with the deep end of the notch 208.Thus, the forward movement of the blade support member 144 is stopped,and the blade 156 is extended from the sheath member 142 as shown inFIGS. 7 and 9.

To retract the blade 156 into the sheath member 142, the tubular member162 is pushed down. The pin 174 is disengaged from the notch 208. Thespace between the pin 174 and the top prong 184 (at the highest reachingpoint of the slots 170,172 at this moment) is aligned to the centralhole 196 and the space between the top and bottom arms 190,192. Sincethe compressed first spring 154 has the tendency to push the bladesupport member 144 and the rod 155 backward, the rod 155 moves out ofthe tubular member 162 and the key member 180 through the slots 170,172,the central hole 196, and the space between the top and bottom arms190,192. Since the pin 174 of the latch mechanism 152 is the onlyobstacle for the rod 155 to overcome, the use of the scalpel 140 is verysmooth. The blade support member 144 can be smoothly moved toward thelatch mechanism 152 until the engagement between the rod 155 and the pin174. For the same reason, after the rod 155 disengaged from the pin, theblade support member 144 can be smoothly moved away from the latchmechanism 152. Accordingly, the latch mechanism 152 substantiallyeliminates the friction forces. The elimination of friction allows saferoperation as well as the correct feel of an instrument.

FIG. 12 shows the scalpel 140 being used by an operator's right hand. Itis appreciated that the scalpel 140 can also be used by an operator'sleft hand by turning the scalpel 180°. When an operator uses the scalpel140, the four big thumbs of the operator's hand grab the externalsurface of the sheath member 142, and the last small thumb leans on theside of the latch mechanism 152. When the operator finishes the use ofthe scalpel 140, the big thumbs turn the scalpel 140 a certain degreewhich is enough for the last small thumb to transversely push thetubular member 162 of the latch mechanism 152 downward as shown in FIG.13. As a result, the blade is to retract into the sheath member 142.

The external surface of the sheath member 142 is knurled so as to allowthe operator to easily grab or turn or control the scalpel 140 during anoperation. In the second embodiment, there is no hole on the externalsurface of the sheath member 142 so that the operator's gloves are notcaught in the holes.

The scalpel 140 can be made of stainless steel. It is preferred,however, that all parts of the scalpel 140 except the blade is made ofplastic materials. The springs 58,76,154,176,402,502 (402,502 see later)are made of metal or metals. However, they can be made of plasticmaterials, or can be coated with a microfilm (e.g. Teflon™) or othertypes of polypropylene materials so that the springs are heat/steamresistent and chemical resistent. Accordingly, almost all parts of thescalpel can be injection molded.

The length of the scalpel 140 is about 5.56 inches (141.22 mm). Thelength of the sheath member 142 and the length of the blade supportmember 144 are about 71.93 mm, respectively. The inclining degree of theramp surface 206 of the rod 155 is about 23°.

In an alternative embodiment, the length of the sheath member 142 islonger than the length of the blade support member 144 whereby in oneembodiment, the blade support member 144 is entirely received in thesheath member 142 when the blade is disposed at its extending position.

Referring now to FIG. 14, there is shown a third embodiment of aretraction scalpel 140', along with the same reference numerals as shownin FIGS. 6-13 for the same parts, generally in accordance with theprinciples of the present invention.

In FIG. 14, a second rod 300 is integral to the back end of the bladereceiving portion 175 (now designated by reference numeral 175') asshown in FIG. 8. The shock absorber 171' (reference numeral 171 in FIG.8) has a central bore to allow the rod 300 to pass through. The rod 300has a similar configuration as the rod 155 shown in FIG. 8. The rod 300includes a tapered front portion 302 having a tip 304 pointed to thelatch mechanism 152. A ramp surface 306 which obliquely faces toward thebottom of the latch mechanism 152 follows the tip 304. The rod 300further includes a notch 308 rearward of the end of the ramp surface306.

When the blade 156 is retracted into the sheath member 142 by theextension force (or return force) of the first spring 154, the taperedfront portion 302 of the rod 300 engages with the pin 174, andeventually, the pin 174 of the latch mechanism 152 drops into the notch308 to lock the blade support member 144 and the blade 156 in place.Accordingly, the blade support member 144 is stopped from further movingforward or backward relative to the latch mechanism 152.

To place the scalpel 140' in an operative position, the latch mechanism152 is pushed downward so as to disengage the pin 174 from the notch 308of the rod 300. The blade support member 144 can then be pushed forward,as described in the first embodiment, to extend the blade 156 out of thesheath member 142.

In the third embodiment, as shown in FIG. 14, a third compression spring310 is disposed outside the rod 300 behind the shock absorber 171'. Whenthe rod 300 is locked in place, the compression spring 310 iscompressed. Accordingly, when the latch mechanism 152 is activated torelease the rod 300, the compression spring 310 helps the rod 300disengage from the pin 174. The third compression spring 310 alsofunctions as a shock absorber when the scalpel is retracted into thesheath member 142. In retracting the blade 156, the return force of thefirst spring 154 overcomes the counteracting force of the fourth spring310 so as to compress the fourth spring 310.

A fourth embodiment is similar to the third embodiment as shown in FIG.14. In the fourth embodiment, the third compression spring 310 iseliminated. The shock absorber 171' is the only shock absorber. Further,when the latch mechanism 152 is activated, the rod 300 is just simplydisengaged from the pin 174. There is no longitudinal spring force todisengage the rod 300 from the latch mechanism 152.

In FIG. 15, a schematic view of another embodiment of a latch mechanism400 is shown (also called fifth embodiment). Comparing to the latchmechanism 152 as shown in FIG. 8, the top portion of the latch mechanism400 is designed to hold a fourth compression spring 402 outside the topportion of the latch mechanism 400. The second spring 176 in FIG. 8,which is disposed inside the latch mechanism 152, is eliminated in thefifth embodiment, but it is functionally replaced by the fourthcompression spring 402.

Further in FIG. 5, the bottom portion of the latch mechanism 402 isbeveled, which is to help the latch mechanism 400 be easily assembledwhile assembling with the blade support member 144, the sheath member142, or other parts of the scalpel.

In FIG. 16, a schematic view of another embodiment of a latch mechanism500 is shown (also called sixth embodiment). Comparing to the latchmechanism 400 as shown in FIG. 15, the top portion of the latchmechanism 500 is integral to a leaf spring 502 instead of using thefourth compression spring 402 as shown in FIG. 15. Two legs of the leafspring 502 biasedly engage with the outer wall of the sheath member 142when the latch mechanism is activated (pushed downward). Accordingly,the leaf spring functions in the same way as that of the fourthcompression spring 402 or the second compression spring 176, toengage/disengage the first rod 155 or the second rod 300 to/from thelatch mechanism 500, 400, 152, respectively.

FIGS. 17-20 illustrate an alternative embodiment of a scalpel 600. Thescalpel 600 includes the same parts as of the scalpel 140 as shown inFIG. 7, except that a back end portion 602 of the tubular sheath member604 has an open end slot 606, and that the key member 608 as shown inFIG. 17 is different from the key member 180 as shown in FIG. 10.

The key member 608 in FIG. 17 is similar to the key member 180 as shownin FIG. 10, except that in FIG. 17, the top prong 610 and the bottomprong 612 are generally identical, and that a post 614 is disposed on atop surface 616 of the top prong 610. In one embodiment, the post 614can be integrally molded on the top surface 616 of the top prong 610.

As shown in FIGS. 19-20, the spring 176 (same reference numeral as shownin FIGS. 8-9) is disposed around the post 614. The spring 176 iscompressed between the top closed end 178 of the tubular member 162 andthe top surface 616 of the top prong 610. Accordingly, the key member608 is longitudinally locked in place. Thus, the key member 608 isprevented from falling out of the back end portion 602 of the sheathmember 604. In FIGS. 19-20, a portion of the bottom prong 612 is cut offfor clearance purposes so that the spring 176 and the post 614 arevisible through an open end 618 of the tubular member 162. It isappreciated that the bottom prong 612 can be the same length as the topprong 610 as shown in FIG. 17.

The open end slot 606 allows the post 614 of the key member 608 to passthrough during the assembly of the scalpel 600. It is appreciated thatother means of assembling of the key member 608 can be used.

In the preferred embodiment, the scalpel is made of plastic materials,such as PVDF, except the blade. The blade and sometimes the springs aremade of metals. In one embodiment, the springs 58,76,154,176,402,504 aremade of plastic materials or are at least coated with a microfilm (e.g.Teflon™) or other types of polypropylene materials so that the springsare heat/steam resistent and chemical resistent. Accordingly, almost allthe parts of the scalpel can be injection molded so that the scalpel isvery light and inexpensive thereby the plastic parts of the scalpel canbe disposable after the use.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

what is claimed is:
 1. A retractable tool holder, comprising:a toolsupport member holding a tool at a front end, including at least onelongitudinally extended slot; a sheath member telescopically at leastpartially receiving the tool support member, the sheath member having aback end and a front end; a first spring being telescopically disposedinside the tool support member proximate a back end of the tool supportmember; a latch mechanism, disposed proximate the back end of the sheathmember, the latch mechanism reciprocating in the slot of the toolsupport member, the movement of the back end of the tool support membertoward the latch mechanism extending the tool out of the sheath memberand compressing the first spring between the back end of the toolsupport member and the latch mechanism, the movement of the back end ofthe tool support member away from the latch mechanism retracting thetool into the sheath member and expanding the first spring between theback end of the tool support member and the latch mechanism; wherein thelatch mechanism includes a member having an open slot, the tool supportmember reciprocates along a longitudinal axis of the tool holder throughthe open slot; and a key member having a prong, disposed proximate theback end of the sheath member, a post being disposed on the prong, asecond spring being disposed between the member and the prong and beingdisposed around the post, so that the key member is prevented fromfalling out of the back end of the sheath member.
 2. A retractable toolholder in accordance with claim 1, wherein the tool is a blade.
 3. Aretractable tool holder in accordance with claim 2, wherein except theblade being made of metal materials, the entire retractable tool holderis made of plastic materials.
 4. A retractable tool holder in accordancewith claim 1, wherein a rod is mounted on the back end of the toolsupport member, the member of the latch mechanism includes means forreleasably locking the rod when the tool support member moves toward thelatch mechanism.